“Pinch me,” says Susan as we cross the Seine from the Left Bank to face the sun-drenched Gothic towers of Notre Dame. “I can’t believe we’re back here.”

We peel off jackets and join the throngs of tourists and worshippers outside the Cathedral. Despite the lyrics of the Cole Porter song — “I love Paris in the summer, when it sizzles” — it’s only April, but the temperature this afternoon sizzles near 80.

We’ve visited Paris at earlier stages of our lives …